This is "permitted" because Amendment XVI grants Congress the power to tax "income" from whatever source derived. Implicitly, it also grants Congress the power to tax the income of any legal entity, although so far its greedy claws have found only individuals and corporations. [Fear not! Leftists are noting if not creative, handed the right weapons.]
The real conservatives on the Court were having none of it:
Our cases establish a clear line between a tax and a penalty: “‘[A] tax is an enforced contribution to provide for the support of government; a penalty . . . is an exaction imposed by statute as punishment for an unlawful act.’” United States v. Reorganized CF&I Fabricators of Utah, Inc., 518 U. S. 213, 224 (1996) (quoting United States v. La Franca, 282 U. S. 568, 572 (1931)). In a few cases, this Court has held that a “tax” imposed upon private conduct was so onerous as to be in effect a penalty. But we have never held—never—that a penalty imposed for violation of the law was so trivial as to be in effect a tax. We have never held that any exaction imposed for violation of the law is an exercise of Congress’ taxing power—even when the statute calls it a tax, much less when (as here) the statute repeatedly calls it a penalty. When an act “adopt[s] the criteria of wrongdoing” and then imposes a monetary penalty as the “principal consequence on those who transgress its standard,” it creates a regulatory penalty, not a tax. Child Labor Tax Case, 259 U. S. 20, 38 (1922).
Too many of the commentators holding (very desperately) forth that Roberts' has "cleverly" boxed the left into a corner have siezed on a syllabus which allows them to indulge their Pollyanna fantasies, of which they will disabuse themselves very quickly if they would simply read the conservative dissent, which is blistering and merciless.
A sample:
The values that should have determined our course to- day are caution, minimalism, and the understanding that the Federal Government is one of limited powers. But the Court’s ruling undermines those values at every turn. In the name of restraint, it overreaches. In the name of constitutional avoidance, it creates new constitutional questions. In the name of cooperative federalism, it undermines state sovereignty. The Constitution, though it dates from the founding of the Republic, has powerful meaning and vital relevance to our own times. The constitutional protections that this case involves are protections of structure. Structural protections—notably, the restraints imposed by federalism and separation of powers—are less romantic and have less obvious a connection to personal freedom than the provisions of the Bill of Rights or the Civil War Amendments. Hence they tend to be undervalued or even forgotten by our citizens. It should be the responsibility of the Court to teach otherwise, to remind our people that the Framers considered structural protections of freedom the most important ones, for which reason they alone were embodied in the original Constitution and not left to later amendment. The fragmentation of power produced by the structure of our Government is central to liberty, and when we destroy it, we place liberty at peril. Today’s decision should have vindicated, should have taught, this truth; instead, our judgment today has disregarded it. For the reasons here stated, we would find the Act in- valid in its entirety. We respectfully dissent
If you knew it was an income tax then why did you say this...
@Because Roberts' opinion also holds that even though the "tax" is not the kind of tax permitted in the first article of the Constitution, and even though the "tax" is also not a tax on incomes covered by Amendment XVI, it is a valid tax (of what kind he does not say) and the existing case law already permits it.
It seems that you're the one coming to an eventual discovery, not me.